Water contamination by the chemicals utilized in today’s technology is a rapidly growing problem globally. A recent studyby the U.S. Centers for Disease Control found that 98 percent of individuals tested had detectable levels of PFAS, a family of particularly long-lasting compounds, also often called ceaselessly chemicals, of their bloodstream.
A brand new filtration material developed by researchers at MIT might provide a nature-based solution to this stubborn contamination issue. The fabric, based on natural silk and cellulose, can remove a wide selection of those persistent chemicals in addition to heavy metals. And, its antimicrobial properties can assist keep the filters from fouling.
The findings are described within the journal ACS Nano, in a paper by MIT postdoc Yilin Zhang, professor of civil and environmental engineering Benedetto Marelli, and 4 others from MIT.
PFAS chemicals are present in a wide selection of products, including cosmetics, food packaging, water-resistant clothing, firefighting foams, and antistick coating for cookware. A recent study identified 57,000 sites contaminated by these chemicals within the U.S. alone. The U.S. Environmental Protection Agency has estimated that PFAS remediation will cost $1.5 billion per yr, in an effort to meet latest regulations that decision for limiting the compound to lower than 7 parts per trillion in drinking water.
Contamination by PFAS and similar compounds “is definitely a really big deal, and current solutions may only partially resolve this problem very efficiently or economically,” Zhang says. “That is why we got here up with this protein and cellulose-based, fully natural solution,” he says.
“We got here to the project by likelihood,” Marelli notes. The initial technology that made the filtration material possible was developed by his group for a totally unrelated purpose — as a solution to make a labelling system to counter the spread of counterfeit seeds, which are sometimes of inferior quality. His team devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” through an environmentally benign, water-based drop-casting method at room temperature.
Zhang suggested that their latest nanofibrillar material could be effective at filtering contaminants, but initial attempts with the silk nanofibrils alone didn’t work. The team decided to try adding one other material: cellulose, which is abundantly available and may be obtained from agricultural wood pulp waste. The researchers used a self-assembly method during which the silk fibroin protein is suspended in water after which templated into nanofibrils by inserting “seeds” of cellulose nanocrystals. This causes the previously disordered silk molecules to line up together along the seeds, forming the idea of a hybrid material with distinct latest properties.
By integrating cellulose into the silk-based fibrils that might be formed right into a thin membrane, after which tuning the electrical charge of the cellulose, the researchers produced a cloth that was highly effective at removing contaminants in lab tests.
The electrical charge of the cellulose, they found, also gave it strong antimicrobial properties. This can be a significant advantage, since one among the first causes of failure in filtration membranes is fouling by bacteria and fungi. The antimicrobial properties of this material should greatly reduce that fouling issue, the researchers say.
“These materials can really compete with the present standard materials in water filtration in the case of extracting metal ions and these emerging contaminants, and so they may outperform a few of them currently,” Marelli says. In lab tests, the materials were capable of extract orders of magnitude more of the contaminants from water than the currently used standard materials, activated carbon or granular activated carbon.
While the brand new work serves as a proof of principle, Marelli says, the team plans to proceed working on improving the fabric, especially by way of durability and availability of source materials. While the silk proteins used may be available as a byproduct of the silk textile industry, if this material were to be scaled up to deal with the worldwide needs for water filtration, the provision could be insufficient. Also, alternative protein materials may prove to perform the identical function at lower cost.
Initially, the fabric would likely be used as a point-of-use filter, something that might be attached to a kitchen faucet, Zhang says. Eventually, it might be scaled up to supply filtration for municipal water supplies, but only after testing demonstrates that this is able to not pose any risk of introducing any contamination into the water supply. But one big advantage of the fabric, he says, is that each the silk and the cellulose constituents are considered food-grade substances, so any contamination is unlikely.
“Most of the conventional materials available today are specializing in one class of contaminants or solving single problems,” Zhang says. “I believe we’re among the many first to deal with all of those concurrently.”
The research team included MIT postdocs Hui Sun and Meng Li, graduate student Maxwell Kalinowski, and up to date graduate Yunteng Cao PhD ’22, now a postdoc at Yale. The work was supported by the Office of Naval Research, the National Science Foundation, and the Singapore-MIT Alliance for Research and Technology.
